An organization gives you a link to its application form. You do not need an account to fill it in — the account comes later, if you are accepted.
Filling it in
The form is in pages, and it saves nothing until you send it, so set aside a few minutes and finish it in one go. Anything marked with an asterisk is required. Some questions only appear once you have answered another one a certain way; that is deliberate, and nothing is hidden from you that applies to you.
If you are asked which positions or crews interest you, pick more than one where you honestly would. A coordinator staffing a weekend has an easier time placing somebody who is open to two things than somebody who is open to one.
After you send it
You get a confirmation email within a few minutes. If it does not arrive, check your junk folder before anything else — a first message from an address you have never received mail from is the classic case for a spam filter.
From there a coordinator reviews applications. How long that takes is up to the organization, not to this software; most tell you on the form itself. You will hear either way.
If you are accepted you get a second email with a link to set a password and finish your account. That link is good for a limited time and can only be used once. If it expires, ask the organization to send another — nobody has to start the application again.
If you are under 18
Organizations set their own minimum age, and some positions have an age minimum of their own — a bar shift is the obvious one.
If you are a minor, the form asks for a parent or guardian's name and email. They get their own email with a link, and your application cannot be approved until they use it to give consent. This is not a formality the organization can waive for you; it is how the organization stays on the right side of the law about holding a minor's information.
If your guardian did not get the email, ask the organization to resend it rather than applying again. A second application makes more work for the person reviewing it and does not make the consent arrive faster.
Changing something you already sent
You cannot edit an application after you send it. Email the organization — every confirmation email has their address in the footer — and say what changed. Once you have an account, you can keep your own details up to date yourself.